Micro-electro mechanical devices (MEMS) attract large attention in many fields of application that include the wireless, automotive and biomedical industries. Reliable RF-MEMS devices have been fabricated utilizing electrostatic and thermal actuation schemes.
The design of microwave and millimeter wave electronics requires components that provide a capability for impedance matching, and/or tuning. Impedance matching is the process through which signals are made to propagate through a high frequency network with a specific amount of reflection, typically as low as possible.
Two of the most common types of components used for impedance matching are capacitors and inductors. Radio frequency micro electromechanical (RF MEMS) techniques have in the past been used to fabricate state-of-the-art tunable capacitors in a variety of different forms. However, to date much less progress has been made in developing RF MEMS tunable inductors.
Prior art in tunable inductors of the RF MEMS type basically consist of topologies in which RF MEMS switches are used to select between different tuning states. Inductors are integral components in RF front end architectures that include filters, matching networks and tunable circuits such as phase shifters. The most common inductor topologies include planar spirals, aircore, and embedded solenoid designs. In comparison to capacitors, however, relatively few tunable inductor configurations have been published; among those presented, many are hybrid approaches that employ MEMS switches to activate different static inductive sections. Furthermore, less attention has been paid to designs that enable control in the sub-nH range as is potentially desirable for matching purposes in applications that use distributed loading of small capacitances, e.g. in loaded-line phase shifters.
Nanocrystalline diamond (NCD) possesses many outstanding material properties such as high thermal conductivity, high stiffness, low thermal expansion coefficient and its chemical inertness prevents from oxidation (up to ˜600° C. in vacuum). These properties of NCD films can be used for high temperature and high power RF-MEMS devices. Furthermore, NCD films also possess low loss when used as a thin film at microwave frequencies.
Accordingly what is needed in the art is an improved tunable inductor of the RF MEMS type.